A polyphenylene ether resin has an excellent mechanical property, electrical property, and thermal resistance, and has an excellent dimensional stability, and therefore it is used in a broad range. However, a processing property of molding thereof by itself is inferior. In order to improve the processing property, the technique of formulating a polyamide therewith is proposed in JP-B-45-997. And at present, it has become a material which has many varied uses.
Recently, an alloy of a polyamide and a polyphenylene ether has been provided with electrical conductivity, and development thereof rapidly progresses for uses as an exterior material of an automobile (a fender, a door panel, etc.) which is possible to be electrostatically coated.
As a property demanding from an exterior material of an automobile, various kinds of properties are mentioned such as electrical conductivity having a level in which electrostatic coating is possible, a low coefficient of linear expansion, thermal resistance, fluidity, etc.
As a technique of providing electrical conductivity having the level in which electrostatic coating is possible, for instance, JP-A-2-201811 discloses a technique of decreasing a value of surface resistance by making a carbon black contained mainly in a polyamide phase. JP-A-4-300296 discloses a technique that a composition comprising a polyamide, a polyphenylene ether, and a carbon black has excellent volume resistivity, fluidity, thermal resistance, and impact strength.
JP-A-8-508534 and U.S. Pat. No. 5,643,502 disclose a composition having excellent impact strength and volume resistivity, by compounding an electrically conductive carbon fibril. And JP-A-8-48869 discloses that a composition having excellent impact strength and volume resistivity can be obtained by compounding an electrically conductive carbon black after compatibilizing a polyamide and a polyphenylene ether.
Further, JP-A-10-310695 discloses a composition having excellent Dart impact strength and electrical conductivity, by using plural polyamides and an electrically conductive carbon black. U.S. Pat. No. 6,221,283 discloses a technique wherein a composition having excellent electrical conductivity can be obtained by restricting the amount of a compatibilizer to that of a specified one.
WO2001/36536 discloses a technique that a composition comprising a polyphenylene ether, a polyamide, a talc, and carbon has excellent electrical conductivity, fluidity, and unnotched Izod impact strength.
Besides these, many applications such as JP-A-2001-302905, JP-A-2002-129023, JP-A-2002-146205, JP-A-2002-146206, JP-A-2002-194207, JP-A-2002-194093, etc were filed.
Recently, in an exterior material of an automobile, an application thereof to an oversized vehicle taken in vision has been studied. In an oversized vehicle, each of parts becomes an oversized scale, and therefore a dimensional change depending on a change of temperature of an outside air is required to be small.
For instance, concerning a material of a fender having a length of 100 cm, when materials having a coefficient of linear expansion of 7×10−5 (° C.−1) and of 9×10−5 (° C.−1) are compared, a difference in dimension of a maximum of about 2 mm will be caused between both of them, when they are compared in a certain condition of temperature [when a difference in temperature is 100° C. (for example, −30° C.˜70° C.)].
This discrepancy affects a clearance with a door etc., and in the worst case, an inconvenience such as contacts when opening or closing the door.
Owing to these factors, when an application to an oversized vehicle is considered, a low coefficient of linear expansion is particularly required.
However, with the above-described techniques, electrical conductivity is provided, but a low coefficient of linear expansion has not been attained, and application to these uses cannot be fully conducted.
On the other hand, as a conventional technique of improving a coefficient of linear expansion in an alloy of a polyamide and a polyphenylene ether, for instance, JP-A-2-163158, JP-A-4-372656, and JP-A-6-306275, discloses that a composition wherein an inorganic filler was formulated is useful. However, with these techniques, a concave and a convex due to an inorganic filler appear on a molded piece, and therefore surface appearance is deteriorated, which is not durable to a practical use.
Further, the techniques of providing electrical conductivity and of making a coefficient of linear expansion low, as seen in the above-described conventional techniques, make compositions fragile, there is a problem that a large amount of swarf which is called as “fines caused by pelletizing” is generated in a pelletizing step (a step wherein a strand extruded from an extruder is cut to form pellets) on processing.
These fines caused by pelletizing, in a place of fabrication, attach to a pellet drier, a pneumatic transportation lines of a molding machine, a hopper part of a molding machine, etc., which necessitates cleaning upon a change of resin type causing greatly decreased productivity. Therefore, this matter of the above arts has been an item always demanded to be improved.
Generally, it is difficult to completely remove these fines caused by pelletizing, and is the sole solution to suppress generation thereof.
The present invention aims to solve the problems which have not been solved by the above stated prior art.
It is therefore an object of the present invention to provide a resin composition, wherein electrical conductivity having a level in which electrostatic coating is possible, a low coefficient of linear expansion and high appearance without lifting of a filler have been accomplished, and further wherein, at the same time, generation of fines caused by pelletizing on extruding has been suppressed.